So thin it's scary, but don't fear, Gyllenhaal fans. Jake isn't sick -- he lost the weight for his role in the upcoming 'Nightcrawler' movie. "I think [I've lost] probably a little over 20 pounds, something like that," he told People on the event's red carpet.

Twenty pounds from his already slender frame is dramatic. Take a good look at his "before" picture above, taken last June. Then scroll down to see the new photos ... IF YOU DARE!